Effect of selenium on hypothyroidism induced by methimazole (MMI) in lactating rats and their pups

The present study was undertaken to assess the effect of selenium (Se) on hypothyroidism induced by methimazole (MMI) in lactating rats and their pups. Rats were randomly divided into four groups of six each: group I served as a negative control which received standard diet; group II received orally MMI (250 mg L–1); group III received both MMI (250 mg L–1, orally) and Se (0.5 mg/kg of diet); group IV served as a positive control and received Se (0.5 mg Na2 SeO3 /kg of diet). Treatments were started from the 14th day of pregnancy until postnatal day 14. In the MMI-exposed group, the body weight of 14-dayold pups diminished compared to controls; besides, a hypertrophy of the thyroid glands was observed. Co-administration of Se through the diet restored these parameters to near normal values. In the MMItreated group, thyroid iodine contents and plasma thyroid hormone levels significantly decreased, while plasma TSH levels increased in pups and their mothers. These biochemical modifications corresponded histologically to closed follicles, increased vascularity and a reduction in colloid volume. Co-treatment with Se ameliorated these parameters. We concluded that the supplementation of Se in diet had beneficial effects on hypothyroidism during a critical period of life